KAJIAN KUALITAS AIR SUNGAI CODE PROPINSI DAERAH ISTIMEWA YOGYAKARTA

Imroatushoolikhah, Dr. Ig. L. Setyawan Purnama, M.Si

2013 | Tesis | S2 Ilmu Lingkungan

Status pencemaran dan beban daya tampung Sungai Code yang besar menunjukkan besarnya bahan pencemar yang masuk ke sungai, selain itu Sungai Code juga merupakan salah satu sungai yang terkena dampak aliran lahar dingin Erupsi Gunungapi Merapi tahun 2010. Erupsi meningkatkan input sedimen dan debit air Sungai Code, serta mengubah substrat dasar perairan. Tujuan penelitian ini : (1) Menganalisis kualitas air Sungai Code secara fisik dan kimia; (2). Membandingkan kualitas air Sungai Code pasca erupsi Merapi 2010 berdasarkan paramater pH, sulfida, dan besi total, dengan kondisi sebelum erupsi; (3). Menganalisis kondisi makrozoobentos pasca erupsi Gunungapi Merapi 2010, serta menganalisis pengaruh kualitas air sungai terhadap makrozoobentos; dan (4). Menganalisis kerugian ekonomi dan mengetahui persepsi terhadap sungai dari sebagian masyarakat yang memanfaatkan air sungai untuk irigasi pertanian dan perikanan keramba. Pengumpulan data dengan metode survei. Lokasi pengambilan sampel ditentukan secara purposive sampling yang mewakili kawasan bagian tengah Sungai Code (sebelum kota dan tengah kota), dan bagian hilir Sungai Code kawasan (setelah kota), meliputi setengah panjang Sungai Code. Hasil penilaian parameter fisik dan kimia air dianalisis di Laboratorium. Sampel makrozoobentos diidentifikasi kemudian dianalisis dengan pendekatan kemelimpahan, dominansi, dan keragaman, serta regresi. Hasil wawancara untuk menilai persepsi masyarakat dan kerugian ekonomi akibat banjir lahar dingin dianalisis dengan crosstab. Hasil penelitian menunjukkan bahwa parameter DO, BOD, COD, dan nitrat, tidak memenuhi baku mutu air kelas I di beberapa lokasi. Adapun kekeruhan, fosfat, dan sulfida, hampir di seluruh lokasi tidak memenuhi baku mutu. Menurunnya kualitas DO, BOD, COD, nitrat, dan fosfat disebabkan oleh limbah yang masuk ke sungai, sedangkan menurunnya kualitas sulfida dan kekeruhan, selain dari limbah juga disebabkan oleh erupsi Merapi. Makrozoobentos yang ditemukan di Sungai Code ada 5 genus yaitu Chironomous, Simulium, Ephemeroptera, Lymnaea, dan Tubifex. Suhu, kecepatan arus dan DO berpengaruh pada menurunnya keragaman dan dominansi bentos. Status Sungai Code pasca erupsi tercemar ringan berdasarkan indeks keragaman bentos = 1,69. Pendapatan masyarakat dari sawah dan perikanan keramba sungai pasca banjir lahar dingin menurun antara Rp.500.000,00-Rp. 2.000.000,00/ responden/ panen.

The amount of pollutants have caused Code River polluted and reduced the capacity of the river. In addition, Code is also one of the affected river flow of Merapi volcano cold lahar in 2010. Eruption have caused massive quantities of flowing water and sediment to enter the river channels emanating from these volcano, as well as changed the riverbed substrate. The purposes of this study are: (1) To analyze the physicochemical quality of Code River water, (2). To compare the quality of Code River water post-eruption of Merapi 2010 with the condition before the eruption based on pH, sulfide, and total iron, (3). To analyze the macrobenthic post-eruption of Merapi Volcano, and then to analyze the effect of water quality on macrobenthic, (4). To analyze the economic losses and the perception from the people who use the river for irrigation farming and fishery cages. Data collection were done by survey method, which the locations were determined by purposive sampling. It represents the middle part of the River Code (before the town and the town center), and the downstream of the Code River (after the town). Water samples were analyzed phisycally and chemically at the Laboratory. Macrobenthic samples were analyzed by approaches of abundance, dominance, and diversity index, as well as regression. The results of interview were analyzed by crosstab to assess public perception and economic losses due to cold lahar flood. Study results showed that the parameters of DO, BOD, COD, and nitrate, did not eligible to the water quality standard Class I in some sites. The turbidity, phosphate, and sulfide, nearly all sites exceeded the quality standards. Declining quality of DO, BOD, COD, nitrate, phosphate caused by the waste that goes into the river, while the decline in the quality of sulfide and turbidity, were caused by both of waste and the eruption of Merapi. Five genus of macrobenthic found in the Code River, Chironomous, Simulium, Ephemeroptera, Lymnaea, and Tubifex. Temperature, water velocity, and DO effected on decreasing diversity and dominance index of macrobenthic. Code River post-eruption categorized into a light polluted showed by diversity index = 1.69. Income from agriculture (rice field) and river-fishery cages after cold lahar flood decreased between Rp 500,0000.00-. 2,000,000.00 / respondent / harvest.

Kata Kunci : kualitas air, Sungai Code, banjir lahar dingin Merapi, makrobentos